As portable electronic devices become more compact, and the amount of information to be processed and stored increases, it has become a significant challenge to design a user interface that allows users to easily interact with the device. This is unfortunate because the user interface is the gateway through which users receive not only content but also responses to user actions or behaviors, including user attempts to access a device's features or tools. Some portable electronic devices (e.g., mobile telephones, sometimes called mobile phones, cell phones, cellular telephones, and the like) have resorted to adding more pushbuttons, increasing the density of push buttons, overloading the functions of pushbuttons, or using complex menu systems to allow a user to access, store and manipulate data. These conventional user interfaces often result in complicated key sequences and menu hierarchies that must be memorized by the user. In addition, as the number of pushbuttons has increased, the proximity of neighboring buttons often makes it difficult for users to activate a desired pushbutton.
Some portable devices now have user interfaces based on a touch-sensitive display (also known as a “touch screen”). The user interacts with a graphical user interface via the touch-sensitive display. The user may operate the interface with a stylus or a digit. Operating a user interface on a touch-sensitive display with a digit (e.g., a finger), however, poses some problems. Because of the relatively small screen sizes on the portable devices, a digit making contact with the touch screen can obscure a sizable portion of the screen and whatever information that is displayed in the obscured portion. Furthermore, operating the interface with a digit may be less precise, because the contact area of a digit with the touch-sensitive display is typically larger than the contact area of a pointed object such as a stylus. This precision problem is particularly acute in text entry applications, where imprecise positioning of the cursor or character insertion marker can make text entry inefficient and frustrate users.
Accordingly, there is need for more efficient ways to position an insertion marker in a touch sensitive display.